1. Field of the Invention
The present invention relates to a fluorescent X-ray analyzer for measuring the content of sulfur in hydrocarbons. More particularly, it relates to a novel fluorescent X-ray analyzer which eliminates analytical error caused by variation of the carbon-hydrogen ratio of the sample.
2. Description of the Prior Art
Heretofore, in typical fluorescent X-ray analyzers, a sample is irradiated by .gamma.-rays or X-rays to measure using a proportional counter fluorescent X-rays generated from sulfur in the sample to measure the weight content of the sulfur in the sample.
FIG. 1 is a block diagram of a conventional fluorescent X-ray analyzer. In FIG. 1, the reference 1 designates an X-ray dector of the energy analyzing type such as a proportional counter. However, it is possible to use a semiconductor detector, a scintillation detector, etc. as the X-ray detector.
The reference 2 designates a radiation source for irradiating the sample such as an X-ray source or a .gamma.-ray source; 3 designates a sample; 4 designates a pulse amplifier; 5 designates a single channel pulse height analyzer; and 6 designates a scaler or a rate-meter.
The pulse signal fed from the X-ray detector 1 is amplified by the pulse amplifier 4 and only pulses resulting from fluorescent X-rays are selected by the pulse height analyzer 5. The pulse rate is measured by the scaler or the rate meter 6. The quantitative analysis of sulfur is conducted by utilizing the fact that the pulse rate is substantially proportional to the weight content of sulfur.
The proportional relation between the pulse count and the sulfur content is the approximation shown in equation (1). An error is caused depending upon the variation of the carbon-hydrogen ratio of the sample of hydrocarbons. ##EQU1## wherein C.H.S; mass of each element, C,H,S in a unit volume of the sample;
.mu.; mass absorption coefficient; PA1 Suffix 1; to irradiated .gamma.-rays; PA1 Suffix 2; to fluorescent X-rays of sulfur; PA1 suffix c,h,s; to each element; PA1 K; efficiency of the apparatus; and PA1 I.sub.1 ; intensity of radiation source (photon/sec)
In equation (1), the incident angle and the reflected angle to the surface of the sample are assumed to be perpendicular to the surface of the sample. In equation (1), if the absorption coefficients for C.H.S. in the denominator are equal, the denominator will be proportional to the density of the sample.
However, the absorption coefficient for H is remarkably low. Accordingly, it is not precisely proportional to the density of the sample. Therefore, the value of equation (1) does not precisely show the weight content.
The energy of the irradiated X-rays and the energy of fluorescent X-rays of sulfur are respectively given as 8 and 2.3 KeV and, when substituted in equation (1), yield equation (1)'. ##EQU2##
The weight content of hydrogen in hydrocarbons is usually in the range of 8 -15% wt. Accordingly, the value of equation (1)' deviates about 6% wt. from the true value according to the variation of the carbon-hydrogen ratio. Thus, as stated above, in a conventional fluorescent X-ray analyzer, the error caused by the variation of the carbon-hydrogen ratio of the sample is detected but the error is not easily correctable.